The present invention relates to internal combustion engine valve timing. More particularly, the present invention relates to adjustable cam sprockets for adjusting engine valve timing of an automotive internal combustion engine.
Most vehicle engines are internal combustion engines that use intake valves to control the entry of combustible gases (i.e. air/gas mixture) into a combustion chamber for ignition by a spark. Following combustion, exhaust valves control the escape of exhaust gases resulting from the combustion. Both the intake valves and the exhaust valves are controlled by cams lobes located on a camshaft. Pistons located in the combustion chamber are driven by the combustion of the combustible gases to cause the rotation of a crankshaft. The crankshaft is used to change the up-and-down motion of the piston into a turning or rotating force. This force is then used to drive the wheels of the vehicle.
The timing of the opening and closing of the intake and exhaust valves relative to the position of the pistons is very important for the operation and performance characteristics of the engine. Optimum performance is achieved when the intake and exhaust valves are operated at a precise position relative to the position of the pistons. A sprocket and chain system is generally used to control the timing of the camshaft rotation (intake and exhaust valve opening) to the crankshaft rotation (piston position). A combination of camshaft sprocket, timing chain and crankshaft sprocket is commonly referred to as a timing set and controls this timing. Adjustment of the rotation of the camshaft relative to the crankshaft of even 1xc2x0 or 2xc2x0 can effect engine performance. For this reason, the timing for an engine is usually a design characteristic of the engine that is determined and fixed by the engine manufacturer. The timing is usually fixed by a positioning xe2x80x9ckeyxe2x80x9d and keyways on both the crank shaft/crank sprocket and the camshaft/cam sprocket or the camshaft/cam sprocket by means of a dowel pin and mating dowel holes.
Determining optimum performance, however, depends upon the particular task for which the engine is being used. The preset engine timing from the manufacturer may be sufficient for a wide range of engine use, but may not be optimum for a particular purpose, such as high performance (long or short racing), off-roading or towing. Advancing the camshaft (by adjusting the camshaft position relative to the crankshaft) increases the lower RPM power. Retarding the camshaft improves the higher RPM power.
Replacement timing sets have been available to replace the original equipment timing set of a vehicle to allow adjustment of the engine timing from the preset manufacturers timing specification. Some of these xe2x80x9cafter marketxe2x80x9d timing sets have a crankshaft sprocket with multiple keyways in its bore. A problem with such a system is that the use is limited to the number of keyways and the fixed timing specification of each keyway. In addition, such timing adjustment systems require that the timing set (either partially or completely) be removed to make the adjustment, adding time and labor to the task. Other adjustment systems provide for adjustment of the camsprocket relative to the camshaft. In many such systems, however, it is also necessary to remove the timing set (either partially or completely) to make the adjustment.
The present invention provides for an adjustable camshaft sprocket assembly for attachment to a camshaft. A camshaft sprocket is removably securable to a camshaft sprocket hub and moveable, independent of the camshaft sprocket hub when the camshaft sprocket assembly is mounted on the camshaft.
An adjustment tool is used to adjust the camshaft sprocket. The camshaft tool is comprised of at least two extensions; the first extension is of a size to fit within one a corresponding opening in the camshaft sprocket hub. The second extension is of a size to pass though a different corresponding opening in the camshaft hub and fit within a corresponding opening in the camshaft sprocket. A handle extension is used for turning the adjustment tool about the first extension, which serves as a pivot.